This invention relates to a developing device using toner as a developer, an image formation apparatus having the developing device, and a computer system including the image formation apparatus.
Also, this invention relates to a developing device used with an electrophotographic image formation apparatus such as a laser printer, a copier, or a facsimile for storing toner and developing a latent image formed on a photoconductor drum in the toner, in particularly, to a structure to fix a roller support frame of the developing device to a housing and to a structure to put a roller support frame, a developing roller, and a regulation blade of the developing device into a unit.
As the image formation apparatus, for example, an image formation apparatus having a developing device for developing a latent image formed on a photoconductor with toner as a developer or the like is known. The image formation apparatus has the developing device placed at a developing position opposed to the photoconductor for developing a latent image formed on the photoconductor to form a toner image in response to an image signal transmitted from an external apparatus such as a host computer.
FIG. 8 shows an example of the developing device. It is a schematic drawing to describe main components of the developing device. The developing device 200 shown in FIG. 8 has a casing 204 for forming a toner storage section 202 storing toner T, a developing roller 206 as a toner supporter supported in the casing 204 for rotation, a toner supply roller 208 as a toner supply member pressed against the developing roller 206 for supplying toner T to the developing roller 206, and a regulation blade 210 as a thickness regulation member for regulating the thickness of the toner T supplied to the developing roller 206.
The developing roller 206 is formed of metal and has a gap with a photoconductor 212. The developing device 200 forms an alternating electric field between the developing roller 206 and the photoconductor 212 and develops a latent image formed on the photoconductor 212 in a noncontact state.
The toner supply roller 208 has an elastic layer of polyurethane foam, etc., placed on the outer peripheral portion of a metal shaft, and is pressed against the developing roller 206 as it is elastically deformed.
The regulation blade 210 has a rubber part 210a and a rubber support part 210b. The rubber support part 210b is attached to the casing 204 via a blade support metal sheet 214. The rubber support part 210b is a thin plate of phosphor bronze, stainless steel, etc., having a spring property and serves as urging member for pressing the rubber part 210a into contact with the developing roller 206.
In the developing device 200, the toner T stored in the toner storage section 202 is supplied by the toner supply roller 208 to the developing roller 206. The supplied toner T has thickness regulated by the regulation blade 210 pressed against the developing roller 206 and is charged by friction and is transported to a developing position opposed to the photoconductor 212. The toner is moved by an alternating electric field formed between the developing roller 206 and the photoconductor 212, whereby a latent image on the photoconductor 212 is developed.
In the developing device 200, to provide a good image, the regulation blade 210 needs to be properly pressed against the developing roller 206 for making uniform the thickness of a toner layer formed on the developing roller 206, and the toner T needs to be charged evenly.
However, to reliably supply the toner T on the developing roller 206, the toner supply roller 208 made of urethane is pressed against the developing roller 206 made of metal. Both end parts of each of the rollers 206 and 208 are regulated by the casing 204 supporting the rollers 206 and 208 and the rollers 206 and 208 are pressed in a direction in which the rollers 206 and 208 approach each other. At this time, in the developing roller 206 and the toner supply roller 208, a force acting in a direction in which the centers are brought away from each other occurs because both ends are regulated. The toner supply roller 208 absorbs the force as urethane is elastically deformed, but the developing roller 206 is a rigid body and thus deflection in a direction in which the center is brought away from the toner supply roller 208 occurs.
When deflection occurs in the developing roller 206, the abutment position of the regulation blade 210 against the developing roller 206 shifts and the regulation blade 210 is not properly against the developing roller 206, making the thickness of the toner layer uneven and also making uneven the charge state by friction of the regulation blade 210, and good developing cannot be conducted.
Also, in a laser printer as an example of the image formation apparatus including a rotary developing unit, a plurality of developing devices storing toners of different colors are set in the rotary developing unit. At the printing time, while the rotary developing unit is rotated, the developing device of the necessary color is brought adjacent to a photoconductor drum. The toner is supplied on a latent image formed on the photoconductor drum and is transferred from the photoconductor drum through a transfer belt to a sheet of print paper, etc., for fixing.
Generally, the developing device has a housing made of a synthetic resin for storing toner and a roller support frame made of metal being fixed to the housing with screws for supporting a developing roller for rotation.
The roller support frame supports the developing roller, and a regulation blade is pressed against the peripheral surface of the developing roller uniformly in the length direction of the regulation blade so as to even toner on the peripheral surface of the developing roller.
However, in the related developing device, the synthetic resin of which the housing is formed has a larger thermal expansion coefficient than the metal of which the roller support frame is formed. When heat generated during the operation of the rotary developing unit conducts to the developing device, the housing is expanded larger than the roller support frame. The roller support frame may become deformed because of the expansion difference between the housing and the roller support frame.
Further, when the roller support frame becomes deformed as mentioned above, the distribution of the press pressure of the regulation blade against the peripheral surface of the developing roller changes in the length direction of the regulation blade. Thus the action of evening the toner by the regulation blade becomes insufficient and a high toner-density portion and a low toner-density portion are produced, causing low-quality print matter to be formed partially with a large density difference.
In the related developing device, the roller support frame is constituted by a frame member extending in parallel with the developing roller and side frame members bent in the same direction at 90 degrees from both ends of the frame member, and is shaped like a character U in cross section. Thus, a force is exerted to the developing roller when the developing roller is placed or removed, the roller support frame may become deformed. Accordingly, although a regulation blade was in contact with the peripheral surface of the developing roller in the length direction thereof at uniform pressure at the beginning, a local point on which pressure is exerted may occur or pressure may be exerted in a varied manner from side to side.
Thus, if the regulation blade cannot be maintained in a state in which it is in contact with the peripheral surface of the developing roller in the length direction thereof at uniform pressure, the evening effect of the regulation blade on the peripheral surface of the developing roller is not demonstrated and therefore the distribution of toner on the developing roller is made uneven, adversely affecting the quality of printed matter.
It is therefore an object of the invention to provide a developing device for making it possible to suppress unevenness of the thickness of a toner layer formed on a developing roller and charge unevenness of toner for conducting good developing, an image formation apparatus having the developing device, and a computer system having the image formation apparatus.
Also, it is other object of the invention to provide a roller support frame fixing apparatus of a developing device and a developing device including the roller support frame fixing apparatus wherein a roller support frame does not become deformed if a housing and the roller support frame are expanded or contracted by heating or cooling assuming that there is a thermal expansion coefficient difference between a material of which the housing is formed and a material of which the roller support frame is formed.
Further, It is still other object of the invention to provide a developing device having a structure for enabling a regulation blade to maintain a state in which the regulation blade is in contact with the peripheral surface of a developing roller in the length direction thereof at uniform pressure, and a rotary developing unit including the developing device.
In order to achieve the above object, according to the present invention, there is provided a developing device comprising:
a toner supporter, which supports toner;
a toner supply member, which is pressed against the toner supporter to supply the toner to the toner supporter; and
a thickness regulation member, which regulates thickness of the toner supplied to the toner supporter by the toner supply member,
wherein the thickness regulation member abuts the toner supporter on the toner supply member side of the toner supporter.
In the above configuration, the thickness regulation member is abutted against the toner supporter from the toner supply member side thereof and thus even if the toner supporter is pressed by the toner supply member and deflection occurs in the toner supporter, it is made possible to abut the thickness regulation member against the toner supporter along the deflection of the toner supporter. Therefore, the thickness regulation member can be properly abutted against the toner supporter and it is made possible to suppress unevenness of the thickness of a toner layer and charge unevenness of toner.
Preferably, the thickness regulation member is provided with a non-abutment part at a tip being far from the abutment position against the toner supporter.
In the above configuration, the tip of the thickness regulation member and the toner supporter form a gap leading to the abutment part. Thus, surplus toner occurring as the toner layer is regulated by the thickness regulation member is accumulated in the gap; when shortage of toner occurs, the accumulated toner is supplied, whereby it is made possible to form a toner layer of uniform thickness.
Preferably, the toner supply member is placed at ahead of the tip of the thickness regulation member in a direction in which the thickness regulation member extends.
In the above configuration, it is made possible to supply toner from the gap at the tip of the toner supply member.
Preferably, the toner supporter is a roller comprised of metal, and the toner supply member is a roller covered an outer peripheral portion thereof with an elastic material.
In the above configuration, the toner supply member can be elastically deformed and pressed against the toner supporter of a rigid body, so that it is made possible to cause the toner supporter to reliably support toner.
Preferably, the developing device further comprising a support member, which supports the toner supporter and the toner supply member at both end sides so that the toner supporter and the toner supply member are urged in a direction of approaching each other.
In the above configuration, it is made possible to reliably abut the toner supply member against the toner supporter without affecting the toner layer formation part of the toner supporter or the toner supply part of the toner supply member.
Here, it is preferable that, the toner supporter and the toner supply member have outer peripheral parts in contact with each other, and ends of the outer peripheral part of the toner supply member are placed inside ends of the outer peripheral part of the toner supporter.
In the above configuration, supply of toner to the end parts of the toner supporter can be suppressed, so that it is made possible to prevent surplus toner from leaking to the end part sides.
Here, it is preferable that, the toner supporter supports the toner supplied from the toner supply member and rotates, and the thickness regulation member abuts the toner supporter in the range of 90 degrees in a rotation direction of the toner supporter from a center of a contact part between the toner supporter and the toner supply member.
In the above configuration, the width of the non-abutment part at the tip of the thickness regulation member becomes almost uniform in the axial direction of the toner supporter and it is made possible to suppress unevenness of pressure produced by the thickness regulation member.
Here, it is preferable that, the thickness regulation member abuts the toner supporter at a position where angle xcex8 between a line connecting a roller axis center of the toner supporter and a roller axis center of the toner supply member and a line connecting the roller axis center of the toner supporter and a center of a contact part between the thickness regulation member and the toner supporter becomes 45 degreesxe2x89xa6xcex8 less than 90 degrees.
In the above configuration, the width of the non-abutment part at the tip of the thickness regulation member becomes furthermore uniform and it is made possible to more suppress unevenness of pressure produced by the thickness regulation member.
Preferably, the toner is supplied by the toner supply member from above a contact part between the toner supporter and the toner supply member in a developable state, and the thickness regulation member abuts the toner supporter below the contact part.
In the above configuration, toner is moved to the toner supply member and the toner supporter by gravitation and is supplied by the toner supply member and is supported on the toner supporter and then it is made possible to regulate the toner by the thickness regulation member, so that it is made possible to form a uniform toner layer unforcibly.
According to the present invention, there is also provided a developing device comprising:
a toner supporter, which supports toner;
a toner supply member, which is pressed against the toner supporter to supply the toner to the toner supporter;
a thickness regulation member, which regulates thickness of the toner supplied to the toner supporter by the toner supply member; and
a support member, which supports the toner supporter and the toner supply member at both end sides so that the toner supporter and the toner supply member are urged in a direction of approaching each other,
wherein the toner supply member is placed at ahead of the tip of the thickness regulation member in a direction in which the thickness regulation member extends,
wherein the thickness regulation member is provided with a non-abutment part at a tip far from the abutment position against the toner supporter;
wherein the toner supporter is a roller comprised of metal;
wherein the toner supply member is a roller covered an outer peripheral portion thereof with an elastic material;
wherein the toner supporter and the toner supply member have outer peripheral parts in contact with each other;
wherein ends of the outer peripheral part of the toner supply member are placed inside ends of the outer peripheral part of the toner supporter;
wherein the thickness regulation member abuts the toner supporter at a position where angle xcex8 between a line connecting a roller axis center of the toner supporter and a roller axis center of the toner supply member and a line connecting the roller axis center of the toner supporter and a center of a contact part between the thickness regulation member and the toner supporter becomes 45 degreesxe2x89xa6xcex8 less than 90 degrees;
wherein the toner is supplied by the toner supply member from above a contact part between the toner supporter and the toner supply member in a developable state; and
wherein the thickness regulation member abuts the toner supporter below the contact part.
In the above configuration, the toner supply member and the toner supporter are urged in the direction of approaching each other and are abutted, whereby it is made possible to supply sufficient toner to the toner supporter. At this time, the toner supply member pressed against the toner supporter made of metal is made an elastic member, whereby while the toner supporter is protected, it is made possible to widen the abutment area of the toner supply member and the toner supporter for enhancing the toner supply property and the toner support property. The roller as the toner supporter and the roller as the toner supply member are supported in end parts and are urged in the support parts, whereby it is made possible to press the toner supply member in a state not affecting the toner layer.
On the other hand, deflection may occur in the toner supporter and the toner supply member urged in both end parts in the direction in which the axial centers are brought away from each other; particularly the toner supporter of a rigid body does not have a member for absorbing the press pressure like the elastic member of the toner supply member and thus there is a tendency to increase deflection. The thickness regulation member abutting the toner supporter varies in contact position and press pressure depending on what position the thickness regulation member abuts the toner supporter at in the circumferential direction of the toner supporter, largely affecting regulation of the thickness of the toner layer. For example, if the thickness regulation member is abutted against the toner supporter on the toner supply member side of the toner supporter so that the tip does not come in contact with the toner supporter, both end sides of the width of the noncontact part at the tip become narrow and the center becomes wide. If the thickness regulation member is abutted against the toner supporter on the opposite side to the toner supply member so that the tip does not come in contact with the toner supporter, both end sides of the width of the noncontact part at the tip become wide and the center becomes narrow. By the way, the noncontact part at the tip forms a gap with the toner supporter and the supplied toner and surplus toner occurring as the toner layer is evened by the thickness regulation member are accumulated in the gap. At this time, if the noncontact part is wide on the end part side of the thickness regulation member toner easily accumulates and the press pressure of the thickness regulation member is affected or there is a fear of the toner leaking to the outside of the developing unit. Thus, the abutment position of the thickness regulation member is placed on the toner supply member side, whereby it is made possible to well regulate the thickness of the toner layer.
Since the gap defined by the tip of the thickness regulation member and the toner supporter becomes the accumulation part of the supplied toner, the gap is placed downstream in the rotation directions of the toner supply member which rotates for supplying toner and the toner supporter for transporting toner, whereby it is made possible to reliably form a toner layer on the toner supporter. That is, the thickness regulation member abuts the toner supporter in the range of 90 degrees in the rotation direction of the toner supporter from the center of the contact position between the toner supporter and the toner supply member, whereby it is made possible to well regulate the thickness of the toner layer to form the toner layer.
Further, the thickness regulation member regulates the thickness of the toner layer on the toner supporter and also charges toner by friction. Thus, it is also important to urge so that the press pressure against the toner supporter becomes uniform in addition to the width of the noncontact part at the tip of the thickness regulation member. Thus, for example, as described above, when deflection occurs in the toner supporter, if the thickness regulation member is abutted against the toner supporter so that the line connecting the axis center of the toner supporter and the toner supply member and the thickness regulation member become parallel, the effect of the deflection is lessened and it is made possible to press the thickness regulation member against the toner supporter almost uniformly and as the abutment part of the toner supporter and the thickness regulation member approaches the abutment part of the toner supporter and the toner supply member, the press pressure in the center lowers. That is, to make uniform the width of the noncontact part at the tip of the thickness regulation member, it is desirable that the abutment part of the toner supporter and the thickness regulation member should be brought dose to the abutment part of the toner supporter and the toner supply member. To make uniform the press pressure of the thickness regulation member against the toner supporter, it is desirable that the thickness regulation member should be abutted against the toner supporter so that the line connecting the axis center of the toner supporter and the toner supply member and the thickness regulation member becomes parallel. Further, to provide the noncontact part at the tip of the thickness regulation member and define a gap by the thickness regulation member and the toner supporter, it is desirable that the abutment position of the thickness regulation member should be brought away from the abutment part of the toner supporter and the toner supply member and the thickness regulation member should be inclined relative to the tangent of the toner supporter in the abutment part of the toner supporter and the toner supply member.
Considering these points, the thickness regulation member is abutted against the toner supporter at the position where the angle xcex8 between the connecting the roller axis center of the toner supporter and the roller axis center of the toner supply member and the line connecting the roller axis center of the toner supporter and the center of the contact part between the thickness regulation member and the toner supporter becomes 45 degreesxe2x89xa6xcex8 less than 90 degrees, whereby it is made possible to better regulate the thickness of the toner layer, press the thickness regulation member against the toner supporter almost uniformly, and suppress unevenness of the thickness of the toner layer and charge unevenness of toner for conducting good developing.
Further, to supply toner without opposing the pull of gravity, toner is supplied from above the toner supporter and the thickness regulation member is abutted against the toner supporter below the abutment part of the toner supporter and the toner supply member, whereby it is made possible to enhance the toner supply property.
According to the present invention, there is also provided an image formation apparatus comprising:
a developing device including:
a toner supporter, which supports toner;
a toner supply member, which is pressed against the toner supporter to supply the toner to the toner supporter; and
a thickness regulation member, which regulates thickness of the toner supplied to the toner supporter by the toner supply member,
wherein the thickness regulation member abuts the toner supporter on the toner supply member side of the toner supporter.
In the above configuration, the proper position of the thickness regulation member can be abutted against the toner supporter and unevenness of the pressure can also be suppressed, so that unevenness of the thickness of the toner layer and charge unevenness of toner can be suppressed and consequently it is made possible to form a high-quality image.
According to the present invention, there is also provided a computer system comprising:
a computer main unit; and
an image formation apparatus, which is connected to the computer main unit, and the image formation apparatus including:
a developing device having:
a toner supporter, which supports toner;
a toner supply member, which is pressed against the toner supporter to supply the toner to the toner supporter; and
a thickness regulation member, which regulates thickness of the toner supplied to the toner supporter by the toner supply member,
wherein the thickness regulation member abuts the toner supporter on the toner supply member side of the toner supporter.
In the above configuration, the proper position of the thickness regulation member can be abutted against the toner supporter and unevenness of the pressure can also be suppressed, so that unevenness of the thickness of the toner layer and charge unevenness of toner can be suppressed and consequently it is made possible to form a high-quality image and it is made possible to provide an excellent computer system as compared with a related art computer system.
According to the present invention, there is also provided an developing device comprising:
a housing, which forms a toner storage section therein, and has a first end face and a second end face; and
a roller support frame, which has a first side frame portion and a second side frame portion for supporting a rotation shaft of a developing roller at corresponding positions on inner sides of the first end face and the second end face of the housing, and the roller support frame being supported in the housing, and the roller support frame being formed of a material which has a smaller thermal expansion coefficient than a material of which the housing is formed,
wherein the roller support frame is fixed integrally on the side of the second side frame portion so that a move of the roller support frame toward the second end face of the housing in a length direction of the rotation shaft of the developing roller is regulated; and
wherein the roller support frame is configured on the side of the first side frame portion so that a relative move of the roller support frame toward the first end face of the housing in the length direction is allowed.
In the above configuration, since the material of which the housing of the developing cartridge is formed has a larger thermal expansion coefficient than the material of which the roller support frame is formed, expansion difference is produced between the housing and the roller support frame (the housing has a larger expansion amount) due to temperature change. However, on the side of the first side frame portion, a relative move of the roller support frame in the length direction to the first end face of the housing is not regulated and thus distortion of the roller support frame caused by the expansion difference between the housing and the roller support frame can be prevented. Therefore, the abutment pressure of the regulation blade against the peripheral surface of the developing roller placed in the roller support frame can be maintained continuously constant in the length direction of the regulation blade and thus it is made possible to supply toner evenly in the length direction.
Preferably, the first side frame portion is formed with an unloaded hole having an inner diameter larger than a diameter of a first screw. The second side frame portion is formed with a screw hole into which a second screw is screwed. The first end face is formed with a screw hole into which the first screw is screwed at a position corresponding to the unloaded hole. The second end face is formed with an unloaded hole having an inner diameter larger than a diameter of the second screw at a position corresponding to the screw hole formed in the second side frame portion. The first screw is screwed into the hole formed in the first end face and pierces the unloaded hole formed in the first side frame portion. The second screw pierces the unloaded hole formed in the second end face and is screwed into the hole formed in the second side frame portion.
In the above configuration, the abutment pressure of the regulation blade against the peripheral surface of the developing roller placed in the roller support frame can be maintained continuously constant in the length direction of the regulation blade and thus it is made possible to supply toner evenly in the length direction.
Here, it is preferable that, the roller support frame supports both end parts of the rotation shaft of the developing roller for rotation through shaft retention members, and the second side frame portion is fastened by the second screw in such a manner that the second end face of the housing is sandwiched between the second side frame portion and the shaft retention member.
In the above configuration, on the side of the second side frame portion of the roller support frame, the roller support frame is fastened by the second screw in such a manner that the second end face of the housing is sandwiched between the second side frame portion and the shaft retention member, and is integrally fixed so that a move of the roller support frame in the length direction to the second end face of the housing is regulated, whereby on the side of the first side frame portion, the roller support frame can make a relative move in the length direction to the first end face of the housing, and distortion of the roller support frame caused by the expansion difference between the housing and the roller support frame can be prevented. Therefore, the abutment pressure of the regulation blade against the peripheral surface of the developing roller placed in the roller support frame can be maintained continuously constant in the length direction of the regulation blade and thus it is made possible to supply toner evenly in the length direction.
Preferably, the first end face and the first side frame portion are formed with at least two screw holes and unloaded holes at corresponding positions, and the second end face and the second side frame portion are formed with at least two unloaded holes and screw holes at corresponding positions.
In the above configuration, at least two screw holes and unloaded holes are made at the corresponding positions, so that the roller support frame can be reliably fixed to the housing.
Preferably, a gap is formed between the first end face of the housing and the first side frame portion of the roller support frame so that a slight gap is formed therebetween in a state that the housing is most contracted.
In the above configuration, if the housing having a larger thermal expansion coefficient is most contracted in an assumed usual operating environment, the end face of the housing can abut the side frame portion of the roller support frame for reliably preventing distortion of the roller support frame.
Preferably, the roller support frame is provided with a regulation blade for evening toner deposited on a peripheral surface of the developing roller.
In the above configuration, unless the roller support frame becomes deformed, the abutment pressure of the regulation blade against the peripheral surface of the developing roller can be maintained continuously constant in the length direction of the regulation blade. Therefore, it is made possible to maintain even toner supply in the length direction.
According to the present invention, there is also provided an image formation apparatus comprising;
a developing device including:
a housing, which has a first end face and a second end face, and the housing forming a toner storage section therein; and
a roller support frame, which has a first side frame portion and a second side frame portion for supporting a rotation shaft of a developing roller at corresponding positions on inner sides of the first end face and the second end face of the housing, and the roller support frame being supported in the housing, and the roller support frame being formed of a material having a smaller thermal expansion coefficient than a material of which the housing is formed,
wherein the roller support frame is fixed integrally on the side of the second side frame portion so that a move of the roller support frame toward the second end face of the housing in a length direction of the rotation shaft of the developing roller is regulated; and
wherein the roller support frame is configured on the side of the first side frame portion so that a relative move of the roller support frame toward the first end face of the housing in a length direction of the rotation shaft of the developing roller is allowed.
In the above configuration, the abutment pressure of the regulation blade against the peripheral surface of the developing roller can be maintained continuously constant in the length direction of the regulation blade and therefore the toner supply state always becomes constant and print of good quality can be accomplished.
According to the present invention, there is also provided a developing device comprising:
a housing, which forms a toner storage section therein; and
a roller support frame, which supports a rotation shaft of a developing roller, and is supported in the housing, and the roller support frame including:
a first side frame portion and a second side frame portion, which supports the rotation shaft of the developing roller;
a lower frame portion, which is connected to both the first and second side frame portions at the bottoms thereof, and supports a regulation blade which abuts a peripheral surface of the developing roller for evening toner deposited on the peripheral surface; and
an upper frame portion, which is connected to both the first and second side frame portions at the tops of the first and second side frame portions, and
wherein both the first and second side frame portions, the lower frame portion and the upper frame portion form a closed loop structure and support the developing roller and the regulation blade as a unit.
In the above configuration, the closed loop structure is adopted, whereby the shape retention of the roller support frame is enhanced, making it hard to deform the roller support frame by the force exerted when the developing cartridge is placed or removed. The regulation blade needs to be uniformly pressed against the peripheral surface of the developing roller in the length direction thereof. As the roller support frame is hard to become deformed as described above, the relationship between the regulation blade and the peripheral surface of the developing roller is maintained continuously. Therefore, any desired toner evening effect can be provided appropriately and inconsistencies in toner density on the developing roller become hard to occur.
Preferably, both the first and second side frame portions and the lower frame portion are molded in one piece.
In the above configuration, both the side frame portions and the lower frame portion can be worked in one piece and are manufactured easily.
Preferably, the upper frame portion is fixed with both the side frame portions by screws.
In the above configuration, the upper frame portion can be added to a related art structure made up of only both side frame portions and a lower frame portion and in addition, only the upper frame portion is later connected additionally, so that the assembling step of the roller support frame is facilitated.
Preferably, the roller support frame is formed of a material having a smaller thermal expansion coefficient than a material of which the housing is formed. The housing has a first end face and a second end face, and the first side frame portion and the second side frame portion are placed at corresponding positions on inner sides of the first end face and the second end face of the housing. The roller support frame is fixed integrally on the side of the second side frame portion so that a move of the roller support frame toward the second end face of the housing in a length direction of the rotation shaft of the developing roller is regulated. The roller support frame is configured on the side of the first side frame portion so that a relative move of the roller support frame toward the first end face of the housing in a length direction of the rotation shaft of the developing roller is allowed.
In the above configuration, since the material of which the housing of the developing cartridge is formed has a larger thermal expansion coefficient than the material of which the roller support frame is formed, expansion difference is produced between the housing and the roller support frame (the housing has a larger expansion amount) due to temperature change. However, according to the described configuration, on the side of the first side frame portion, a relative move of the roller support frame in the length direction to the first end face of the housing is not regulated and thus distortion of the roller support frame caused by the expansion difference between the housing and the roller support frame can be prevented. Therefore, according to the invention, the abutment pressure of the regulation blade against the peripheral surface of the developing roller placed in the roller support frame can be maintained continuously constant in the length direction of the regulation blade and thus it is made possible to supply toner evenly in the length direction.
Here, it is preferable that, the first side frame portion is formed with an unloaded hole having an inner diameter larger than a diameter of a first screw. The second side frame portion is formed with a screw hole into which a second screw is screwed. The first end face is formed with a screw hole into which the first screw is screwed at a position corresponding to the unloaded hole. The second end face is formed with an unloaded hole having an inner diameter larger than a diameter of the second screw at a position corresponding to the screw hole formed in the second side frame portion. The first screw is screwed into the hole formed in the first end face and pierces the unloaded hole formed in the first side frame portion. The second screw pierces the unloaded hole formed in the second end face and is screwed into the hole formed in the second side frame portion.
In the above configuration, the abutment pressure of the regulation blade against the peripheral surface of the developing roller placed in the roller support frame can be maintained continuously constant in the length direction of the regulation blade and thus it is made possible to supply toner evenly in the length direction.
Here, it is preferable that, the roller support frame supports both end parts of the shaft of the developing roller for rotation through shaft retention members, and the second side frame portion is fastened by the second screw in such a manner that the second end face of the housing is sandwiched between the second side frame portion and the shaft retention member.
In the above configuration, on the side of the second side frame portion of the roller support frame, the roller support frame is fastened by the second screw in such a manner that the second end face of the housing is sandwiched between the second side frame portion and the shaft retention member, and is integrally fixed so that a move of the roller support frame in the length direction to the second end face of the housing is regulated, whereby on the side of the first side frame portion, the roller support frame can make a relative move in the length direction to the first end face of the housing, and distortion of the roller support frame caused by the expansion difference between the housing and the roller support frame can be prevented. Therefore, the abutment pressure of the regulation blade against the peripheral surface of the developing roller placed in the roller support frame can be maintained continuously constant in the length direction of the regulation blade and thus it is made possible to supply toner evenly in the length direction.
According to the present invention, there is also provided a rotary developing unit comprising:
a plurality of developing device, each including:
a housing, which forms a toner storage section therein; and
a roller support frame, which supports a rotation shaft of a developing roller, and being supported in the housing, and the roller support frame including:
a first side frame portion and a second side frame portion for supporting the rotation shaft of the developing roller;
a lower frame portion, which is connected to both the first and second side frame portions at the bottoms thereof, and supports a regulation blade which abuts a peripheral surface of the developing roller for evening toner deposited on the peripheral surface, and
an upper frame portion, which is connected to both the first and second side frame portions at the tops of the first and second side frame portions,
wherein both the first and second side frame portions, the lower frame portion and the upper frame portion form a closed loop structure and support the developing roller and the regulation blade as a unit; and
wherein the plurality of developing devices are placed so as to rotate around a rotation shaft of the rotary developing unit.
In the above configuration, the operation of rotating the rotary developing unit on the rotation shaft thereof for bringing the developing cartridge of any desired color adjacent to the photoconductor drum for developing is repeated with a plurality of developing cartridges, whereby toner color images are formed on the photoconductor drum and color print can be executed. At the time, it is hard to deform the roller support frame by the external force exerted when the developing cartridge is placed in or removed from the rotary developing unit, so that the relationship between the regulation blade and the peripheral surface of the developing roller is maintained, any desired toner evening effect can be provided appropriately, and inconsistencies in toner density on the developing roller become hard to occur.
According to the present invention, there is also provided an image formation apparatus comprising:
a rotary developing unit including:
a plurality of developing device, each having:
a housing, which forms a toner storage section therein; and
a roller support frame, which supports a rotation shaft of a developing roller, and is supported in the housing, and the roller support frame including:
a first side frame portion and a second side frame portion for supporting the rotation shaft;
a lower frame portion which is connected to both the first and second side frame portions at the bottoms thereof, and supports a regulation blade which abuts a peripheral surface of the developing roller for evening toner deposited on the peripheral surface; and
an upper frame portion, which is connected to both the first and second side frame portions at the tops of the first and second side frame portions, and
wherein both the first and second side frame portions, the lower frame portion and the upper frame portion form a closed loop structure and support the developing roller and the regulation blade as a unit; and
wherein the plurality of developing devices are placed so as to rotate around a rotation shaft of the rotary developing unit.
In the above configuration, the relationship between the regulation blade and the peripheral surface of the developing roller is maintained, any desired toner evening effect can be provided appropriately, and inconsistencies in toner density on the developing roller become hard to occur.